With 2015 looking like it could be a repeat of 2014, growers might fear the worst. Following last season there’s an ample supply of Septoria inoculum and with little in the way of a winter to check disease; crops are at risk from the combined threat of Septoria and yellow rust.
That may cause some to think of beefing up early season disease control compared to previous seasons but Ben Giles of Bayer CropScience questions whether that is really necessary. “We saw last season that well-timed, robust T0 and T1 sprays performed well and I would be reluctant to move away from current recommendations,” he says.
Based on data from the company’s Hinton Waldrist site, that current recommendation is an effective T0 using CTL for Septoria and a fast moving azole if yellow rust is a risk, and a second protective coating of CTL with Proline275 at T1.
“Our central location means we see both diseases but across 30 varieties we still achieved good control, regardless of resistance rating. The T0 is a holding spray. Its purpose is to manage Septoria inoculum by reducing spore development on the lower leaves. It helps buy time if T1’s are delayed by the weather, and is a proven low-cost investment.
“A fast moving azole such as tebuconazole or cyproconazole is there to manage yellow rust. Using a primary azole such as prothioconazole or epoxiconazole at the T0 timing is unnecessary and will only increase selection pressure on these key triazoles.”
And the same basically applies to new-generation SDHI at T1 he says. “You only need the curative potency of a product like Aviator 235Xpro at T1 if the T0 spray has been missed or the T1 timing has been delayed, otherwise save it until the more yield responsive T2.”
Whilst there has been a lot of talk of CTL being used at T2, historically there has been very little used at this timing. It is important to remember that CTL is a protectant only. “Use protectants where they work best, at protective timings! This is why CTL is such an important component of well timed T1 applications. When you combine it with a broad spectrum azole such as
prothiocionazole you’ve got two modes of action protecting leaf three – the primary target – and prothioconazole gives you activity against the stem complex and mildew too. If you look at our programme data we saw no difference from Proline275 + CTL v SDHI at T1. Both delivered an average yield response of over 4.5t/ha as part of our recommended four spray programme.”
In a standard 4 spray programme Proline275 + CTL and Aviator 235Xpro perform equally at T1
Average of four independent trials in 2014. Average untreated yield 8.8 (t/ha) Average disease pressure across L1+ 2 = 60%.
Treated programme; T0 - Folicur 0.4 L/ha + CTL 1.0 L/ha
T2 - Aviator 235Xpro 1.0 L/ha T3 - Proline275 0.55 L/ha.